I'd like to know what is our rule for romanizing and spacing Japanese verbs comprised of 'main verb(て-form) + auxiliary verb' like
Oshiete + Kudasai / Shite + Iru / Yonde + Miru /...
of course when there is no official romaji writing.

*て-form (音便形)
The last letter of verbs end with te(て) or de(で) like
教える(Oshieru) > 教えて (Oshiete)
進む(Susumu) > 進んで (Susunde)